Wireless communication devices such as User Equipments (UE) are also known as e.g. wireless terminals, mobile terminals and/or mobile stations. Wireless communication devices are enabled to communicate or operate wirelessly in a Heterogeneous wireless communication system comprising multiple networks or Heterogeneous Networks (HetNet) with access nodes, such as a cellular communications network comprising Second/Third Generation (2G/3G) network, 3G Long Term Evolution (LTE) network, Worldwide interoperability for Microwave Access (WiMAX) network, etc.
Wireless communication devices may further be referred to as mobile telephones, cellular telephones, smart phones, laptops, tablet computers or phablets with wireless capability, just to mention some further examples. The wireless communication device in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data via an access node with another entity, such as another communication device or a server in the wireless communication system.
When a wireless communication device camping in an LTE network starts a Circuit Switched (CS) service, such as a voice call, it sends a CSFB request to a Mobility Management Entity (MME) via an access node, e.g. an Ehanced NodeB (eNB) in the LTE network. The CSFB is a technology whereby voice services and Short Message Services (SMS) are delivered to LTE communication devices through the use of Global System for Mobile Communications (GSM) or other circuit-switched 2G/3G networks such as Universal Mobile Telecommunications System (UMTS), Code division multiple access (CDMA) 2000 etc. The CSFB is needed because the LTE network is a packet-based all-IP (Internet Protocol) network that cannot support circuit-switched calls. When an LTE communication device is used to make or receive a voice call or SMS, the communication device may “fall back” to the 3G or 2G network to complete the call or to deliver the SMS text message.
After receiving the CSFB request from the wireless communication device, the MME sends a response with target 2G/3G cell data such as frequency for carrying out the CS service, to the wireless communication device via the eNB, which redirects the wireless communication device to the 2G/3G network to carry out the CS service.
A problem arises when the wireless communication device does not get the response with the target CS cell data from the MME or eNB of the LTE network. This may happen when the wireless communication device is at a coverage edge of an LTE network cell where the message exchange between the wireless communication device and the LTE network is not reliable. The problem becomes more serious especially when the LTE network generally prefers the wireless communication device to camp in the LTE network over the 2G/3G network.